Slow aggregate query with join on same table - mysql

Question

I have a query to show customers and the total dollar value of all their orders. The query takes about 100 seconds to execute.
I'm querying on an ExpressionEngine CMS database. ExpressionEngine uses one table exp_channel_data, for all content. Therefore, I have to join on that table for both customer and order data. I have about 14,000 customers, 30,000 orders and 160,000 total records in that table.
Can I change this query to speed it up?
SELECT link.author_id AS customer_id,
customers.field_id_122 AS company,
Sum(orders.field_id_22) AS total_orders
FROM exp_channel_data customers
JOIN exp_channel_titles link
ON link.author_id = customers.field_id_117
AND customers.channel_id = 7
JOIN exp_channel_data orders
ON orders.entry_id = link.entry_id
AND orders.channel_id = 3
GROUP BY customer_id
Thanks, and please let me know if I should include other information.
UPDATE SOLUTION
My apologies. I noticed that entry_id for the exp_channel_data table customers corresponds to author_id for the exp_channel_titles table. So I don't have to use field_id_117 in the join. field_id_117 duplicates entry_id, but in a TEXT field. JOINING on that text field slowed things down. The query is now 3 seconds
However, the inner join solution posted by #DRapp is 1.5 seconds. Here is his sql with a minor edit:
SELECT
PQ.author_id CustomerID,
c.field_id_122 CompanyName,
PQ.totalOrders
FROM
( SELECT
t.author_id
SUM( o.field_id_22 ) as totalOrders
FROM
exp_channel_data o
JOIN
exp_channel_titles t ON t.author_id = o.entry_id AND o.channel_id = 3
GROUP BY
t.author_id ) PQ
JOIN
exp_channel_data c ON PQ.author_id = c.entry_id AND c.channel_id = 7
ORDER BY CustomerID

Answer 1

If this is the same table, then the same columns across the board for all alias instances.
I would ensure an index on (channel_id, entry_id, field_id_117 ) if possible. Another index on (author_id) for the prequery of order totals
Then, start first with what will become an inner query doing nothing but a per customer sum of order amounts.. Since the join is the "author_id" as the customer ID, just query/sum that first. Not completely understanding the (what I would consider) poor design of the structure, knowing what the "Channel_ID" really indicates, you don't want to duplicate summation values because of these other things in the mix.
select
o.author_id,
sum( o.field_id_22 ) as totalOrders
FROM
exp_channel_data customers o
where
o.channel_id = 3
group by
o.author_id
If that is correct on the per customer (via author_id column), then that can be wrapped as follows
select
PQ.author_id CustomerID,
c.field_id_122 CompanyName,
PQ.totalOrders
from
( select
o.author_id,
sum( o.field_id_22 ) as totalOrders
FROM
exp_channel_data customers o
where
o.channel_id = 3
group by
o.author_id ) PQ
JOIN exp_channel_data c
on PQ.author_id = c.field_id_117
AND c.channel_id = 7

Answer 2

Can you post the results of an EXPLAIN query?
I'm guessing that your tables are not indexed well for this operation. All of the columns that you join on should probably be indexed. As a first guess I'd look at indexing exp_channel_data.field_id_117

Answer 3

Try something like this. Possibly you have error in joins. also check whether joins on columns are correct in your databases. Cross join may takes time to fetch large data, by mistake if your joins are not proper on columns.
select
link.author_id as customer_id,
customers.field_id_122 as company,
sum(orders.field_id_22) as total_or_orders
from exp_channel_data customers
join exp_channel_titles link on (link.author_id = customers.field_id_117 and
link.author_id = customer.channel_id = 7)
join exp_channel_data orders on (orders.entry_id = link.entry_id and orders.entry_id = orders.channel_id = 3)
group by customer_id